docs: def export_html(self, pathname):
          """
          Export notebook to .html file
          :param pathname: output filename
          :return:
          """
  
          html_exporter = HTMLExporter()
  
          (body, resources) = html_exporter.from_notebook_node(self.nb)
  
          if pathname == '-':
              sys.__stdout__.write(body)
          else:
              with open(pathname, 'w') as f:
                  f.write(body)
  
          logging.info("HTML notebook exported to '{}'".format(pathname))